Digital Beamforming Array Antenna Research Articles

Concurrent Dual -Band T/R/Calibration Switch Module With Quasi-Elliptic Dual-Bandpass Frequency Response Implementing Metamaterial Transmission Line and Negative Resistance

A novel dual-band transmit/receive (T/R) switch module with an integrated calibration path, hereafter a T/R/Calibration switch module, is developed for dual $K/Ka$ -band array systems, especially digital beam-forming antenna array system, using 0.18- $\mu{\hbox{m}}$ BiCMOS technology. A unique quasi-elliptic dual-bandpass frequency response is achieved in its reception and calibration paths with the use of a composite right/left-handed metamaterial transmission line structure coupled with the Colpitts-style negative-resistance generation circuit. The proposed T/R/Calibration switch module architecture provides a self-calibration for both transmission and reception from the farthest end of an array transceiver excluding antennas, thereby offering an accurate calibration function for the synthetic aperture radar consequently. The newly proposed T/R/Calibration switch topology enhances the opportunity of standalone operation of multi-band array transceivers by the integrated self-calibration capability, while still fulfilling the low-noise and high-power needed for the transceivers for reception and transmission via bidirectional low-noise amplifier/power amplifier, respectively.

English

The element failure of digital beam forming array antenna systems used in defence equipment increases the side lobe power level which distorts the beam pattern of the antenna array. The problem of array failure correction becomes more complex when null steering conditions are required to be added. In this paper, the problem of linear antenna array failure has been addressed with multiple wide band null steering using firefly algorithm (FA) by controlling the amplitude and phase excitation of array elements. A fitness function in the form of template has been formulated to obtain the error between original (pre-failed) side lobe pattern and measured side lobe pattern and this error function has been minimized using FA. Numerical example of element failure correction of element failure of array along with multiple nulls is presented to show the capability of this flexible approach. Defence Science Journal, 2014, 64(2), pp. 136-142. DOI: http://dx.doi.org/10.14429/dsj.64.4250

Comparison of Correction Techniques and Analysis of Errors for Digital Beamforming Antenna Array With Single RF Receiver

A new correction method is proposed for the single RF channel digital beamforming (DBF) antenna array. In this array, each array element is followed by a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$0/\pi$</tex></formula> phase shifter, and the element outputs can be recovered by the single channel through the time sequence phase weighting (TSPW) technique. The outputs can be used to form desired beams through DBF. The performance of the DBF is influenced by the imperfection of the phase shifters. To obtain the errors in each phase shifter, the online test method based on a single known plane wave is introduced. The online test results are used to correct the element outputs using the relationship between the actual and the incorrect outputs. Compared with another previously proposed correction method, the new method is simpler and more suitable for real time correction. The factors that may influence the capability of the correction are analyzed. To validate the proposed method, an eight-element prototype is measured, and the data are used to synthesize low sidelobe patterns. Results show that the sidelobe level and gain improvements after correction are 11.1 and 2.6 dB, respectively.

Grating Lobe Reduction in a Phased Array of Limited Scanning

Amplitude and phase weighting at the subarray outputs alone causes grating lobes (GLs) in the array factor. A combined approach to disrupt the periodicity in the array is proposed to reduce the GLs. In this approach, three measures are simultaneously used. They are: (1) the optimized amplitude weighting at the subarray ports; (2) using the random subarray; and (3) the random staggering of the rows. The optimization was carried out by using genetic algorithms (GAs). The 24 (along X) times 32 (along Y) phased array was designed to verify the proposed approach. Along Y, the scan range is (-10deg, +10deg) and the subarrays are used. Along X, the scan range is (-45deg, +45deg) without using the subarrays. The comparison was done through array factor. In the whole two dimensional scan space, the simulated results show that the GL is -3.77 dB when using the conventional array, -4.28 dB when using (1) alone, -11 dB when using (2) alone, -14 dB when using (3) alone, -20 dB when using the combined approach proposed in this paper. This approach can be used for a phased array with limited scanning and for the digital beamforming antenna array with adaptive nulling.